3Com Switch 7700 Configuration Manual page 107

Before RIP completely deletes an unreachable route from the routing table, it
advertises the route by sending four update packets with route metric of 16, to let
all the neighbors knows that the route is unreachable. Routes do not always
become unreachable when a new period starts so the actual value of the
garbage-collection timer is 3 to 4 times the value of the period update timer.
You must consider network performance when adjusting RIP timers, and configure
all the routes that are running RIP, so as to avoid unnecessary traffic or network
oscillation.
Configuring RIP-1 Zero Field Check of the Interface Packet
According to the RFC1058, some fields in the RIP-1 packet must be 0. When an
interface version is set to RIP-1, the zero field check must be performed on the
packet. If the value in the zero field is not zero, processing is refused. There are no
zero fields in RIP-2 packets so configuring a zero field check is invalid for RIP-2.
Perform the following configurations in RIP view.
Table 11 Configuring Zero Field Check of the Interface Packet
Operation
Configure zero field check on the RIP-1 packet checkzero
Disable zero field check on the RIP-1 packet
By default, RIP-1 performs zero field check on the packet.
Specifying the Operating State of the Interface
In the VLAN interface view, you can specify whether RIP update packets are sent
and received on the interface. In addition, you can specify whether an interface
sends or receives RIP update packets.
Perform the following configuration in VLAN interface view.
Table 12 Specifying the Operating State of the Interface
Operation
Enable the interface to run RIP
Disable RIP on the interface
Enable the interface to receive RIP update
packets
Disable receipt of RIP update packets on the
interface
Enable the interface to send RIP update
packets
Disable transmission of RIP packets on the
interface
The rip work command is functionally equivalent to both rip input and rip
output commands.
By default, all interfaces except loopback interfaces both receive and transmit RIP
update packets.
Command
undo checkzero
Command
rip work
undo rip work
rip input
undo rip input
rip output
undo rip output
RIP 99